The present invention relates to aircraft valves and instrumentation and control equipment and, more particularly, to an improved integrated cabin pressure control system valve that includes an improved instrumentation and control circuit.
For a given airspeed, an aircraft may consume less fuel at a higher altitude than it does at a lower altitude. In other words, an aircraft may be more efficient in flight at higher altitudes as compared to lower altitudes. Moreover, bad weather and turbulence can sometimes be avoided by flying above such weather or turbulence. Thus, because of these and other potential advantages, many aircraft are designed to fly at relatively high altitudes.
As the altitude of an aircraft increases, the ambient pressure outside of the aircraft decreases and, unless otherwise controlled, excessive amounts of air could leak out of the aircraft cabin causing it to decompress to an undesirably low pressure. If the pressure in the aircraft cabin is too low, the aircraft passengers may suffer hypoxia, which is a deficiency of oxygen concentration in human tissue. The response to hypoxia may vary from person to person, but its effects generally include drowsiness, mental fatigue, headache, nausea, euphoria, and diminished mental capacity.
Studies have shown that the symptoms of hypoxia may become noticeable when cabin pressure altitude is above the equivalent of 8,000 feet. Thus, many aircraft are equipped with a cabin pressure control system to, among other things, maintain the cabin pressure altitude to within a relatively comfortable range (e.g., at or below approximately 8,000 feet) and allow gradual changes in the cabin pressure altitude to minimize passenger discomfort.
In addition to a control system for maintaining cabin pressure altitude, regulations promulgated by various governmental certification authorities require that aircraft be equipped with specified indications and/or warnings to alert pilots to a decompression event. In particular, these regulations require that pilots be provided with an indication of actual cabin pressure altitude, and the differential pressure between cabin pressure altitude and actual pressure altitude outside of the aircraft. These regulations also require that the pilots be provided with a visual or audible warning, in addition to the indications, of when the differential pressure and cabin pressure altitude reach predetermined limits. Moreover, in order for an aircraft to be certified for flights above 30,000 feet, it must include oxygen dispensing units that automatically deploy before the cabin pressure altitude 15,000 feet.
In order to meet the above-noted requirements for alarm, indication, and oxygen deployment, various types of systems and equipment have been developed. For example, some systems have included analog-pneumatic gages and aneroid switches, audible alarms, warning lights, and/or color coded messages. One particular system, known as a cabin pressure acquisition module (CPAM), is a stand-alone component that uses a single pressure sensor to provide the alarm, indication, and oxygen deployment capabilities. In addition, some cabin pressure control systems are designed to not only perform cabin pressure control operations, but to use the pressure sensor within the cabin pressure control system to provide the same alarms, indications, and oxygen deployment functions as the CPAM.
Aircraft and the cabin pressure control systems installed on aircraft are robustly designed and manufactured, and are operationally safe. Nonetheless, in addition to providing the alarm, indication, and oxygen deployment functions noted above, certification authorities also require that aircraft be analyzed for certain events that may occur under certain, highly unlikely conditions. For example, one particular type of hypothetical event that aircraft may be analyzed for is known as a xe2x80x9cgradual decompression without indication.xe2x80x9d In analyzing such an event, a component failure is postulated that causes the cabin of the aircraft to gradually decompress. In addition, the system that provides the alarm, indication, and oxygen deployment functions is also postulated to fail, resulting in a hypothetical loss of indication and/or warning of the decompression, and no oxygen deployment.
Previously, the gradual decompression without indication event was classified by certification authorities as a xe2x80x9cmajorxe2x80x9d event. This meant that the probability of the event was less than one occurrence per 1,000,000 flight hours (e.g., 10xe2x88x926 event/flight-hour). Certification authorities have recently changed the classification of this event to a xe2x80x9ccatastrophicxe2x80x9d event. A catastrophic event is one in which the probability less than one occurrence per billion flight-hours (e.g., 10xe2x88x929 event/flight-hour).
One particular design option that may be implemented to meet the above regulations is to use a CPAM in combination with a cabin pressure control system. To reduce the likelihood of common mode failure, the two systems may use different transmission methods to output the information for alarm, indication, and oxygen deployment (e.g., one system may use ARINC 429 protocol, the other may use RS422 protocol). This implementation, while it may reduce the likelihood for the gradual decompression without indication event to less than 10xe2x88x929 event/flight-hour, also presents certain drawbacks. In particular, this implementation may result in substantially increased costs and aircraft down time associated with installation, integration, and maintenance. It may also result in increased aircraft weight and reduced space.
Hence, there is a need for an aircraft pressure control system that provides the necessary alarm, indication, and oxygen deployment functions, that is designed in a manner to meet stringent safety guidelines for a gradual decompression without indication event, and that does not substantially increase installation, integration, and maintenance costs, and/or does not significantly increase aircraft weight, and/or does not take up additional space within the aircraft. The present invention addresses one or more of these needs.
The present invention provides an instrumentation and control circuit that uses multiple, dissimilar sensors and signals for warnings, indications, and controls, and that may be used with an integrated cabin pressure control system valve. The circuit is designed to reduce the likelihood of a gradual decompression without indication event, and does not result in substantially increased installation, integration, and maintenance costs, and/or does not significantly increase aircraft weight, and/or does not take up additional space within the aircraft.
In one embodiment of the present invention, and by way of example only, an aircraft cabin pressure control valve includes a valve body, a valve, at least two controller circuits, and a valve actuator. The valve is mounted in the valve body and is moveable between a closed and open position. The controller circuits are mounted on the valve body, and are operable to sense the cabin pressure and supply a valve actuation signal. The valve actuator is mounted on the valve body and is operable, in response to one or more of the valve actuation signals, to position the outflow valve to any one of the plurality of positions. Each of the controller circuits includes a first pressure sensor, a second pressure sensor, a digital signal conditioning circuit, an analog signal conditioning circuit, and a processor. The first pressure sensor is operable to sense aircraft cabin pressure and supply a first pressure signal representative thereof. The second pressure sensor is dissimilar from the first pressure sensor and is operable to sense aircraft cabin pressure and supply a second pressure signal representative thereof. The digital signal conditioning circuit is coupled to receive the first pressure signal and is operable, in response thereto, to supply a digital pressure signal. The analog signal conditioning circuit is coupled to receive the second pressure signal and is operable, in response thereto, to supply an analog pressure signal. The processor is coupled to receive the analog pressure signal and the digital pressure signal and is operable, in response thereto, to supply at least (i) a signal representative of cabin pressure altitude and (ii) the valve actuation signal.
In another embodiment, a circuit for supplying one or more signals representative of an aircraft cabin environment includes a first pressure sensor, a second pressure sensor, a digital signal conditioning circuit, an analog signal conditioning circuit, and a processor. The first pressure sensor is operable to sense aircraft cabin pressure and supply a first pressure signal representative thereof. The second pressure sensor is dissimilar from the first pressure sensor and is operable to sense aircraft cabin pressure and supply a second pressure signal representative thereof. The digital signal conditioning circuit is coupled to receive the first pressure signal and is operable, in response thereto, to supply a digital pressure signal. The analog signal conditioning circuit is coupled to receive the second pressure signal and is operable, in response thereto, to supply an analog pressure signal. The processor is coupled to receive the analog pressure signal and the digital pressure signal and is operable, in response thereto, to supply at least a signal representative of cabin pressure altitude.
In still another embodiment, a controller circuit for controlling the position of a cabin pressure control system outflow valve includes a first pressure sensor, a second pressure sensor, a digital signal conditioning circuit, an analog signal conditioning circuit, and a processor. The first pressure sensor is operable to sense aircraft cabin pressure and supply a first pressure signal representative thereof. The second pressure sensor is dissimilar from the first pressure sensor and is operable to sense aircraft cabin pressure and supply a second pressure signal representative thereof. The digital signal conditioning circuit is coupled to receive the first pressure signal and is operable, in response thereto, to supply a digital pressure signal. The analog signal conditioning circuit is coupled to receive the second pressure signal and is operable, in response thereto, to supply an analog pressure signal. The processor is coupled to receive the analog pressure signal and the digital pressure signal and is operable, in response thereto, to supply at least (i) a signal representative of cabin pressure altitude and (ii) the valve actuation signal.
In yet another embodiment of the present invention, a method of determining cabin pressure altitude in an aircraft cabin includes the steps of determining cabin pressure using a first pressure determination method, determining cabin pressure using a second pressure determination method that is different from the first pressure determination method, and determining cabin pressure altitude based on the cabin pressure determined using at least one of the first and the second pressure determination methods.
In yet still a further embodiment, in an aircraft cabin pressure control system having an outflow valve that is used to control cabin pressure in an aircraft, a method of controlling outflow valve position includes the steps of determining the cabin pressure using a first pressure determination method, determining the cabin pressure using a second pressure determination method that is different from the first pressure determination method, determining cabin pressure altitude based on the cabin pressure determined using at least one of the first and the second pressure determination methods, and controlling the position of the outflow valve based on the determined cabin pressure altitude.
Other independent features and advantages of the preferred circuit and valve will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.